FIG. 1 shows schematically a typical command and control system for a small naval vessel. One essential function of such a system is to organise and present to the Commanding Officer the information he requires in order to make tactical decisions concerning the allocation of weapons to targets and for manoeuvring the ship. This information is derived from sensors on board the ship such as the surveillance radar and sonar, and also from encyclopaedic data and from external sources including sensors on other ships or aircraft, transmitted via a data link. Information is presented on an electronic graphical display console in the form of a plan view display of the world around the ship.
Factors which have to be considered by the commander to manoeuvre his ship in a practical battle situation include weapon and sensor blind arcs, the direction, range and speed of approach of threats and the positions of other vessels which may pose a risk of collision. For example a missile system mounted at the back of a ship cannot be used to engage targets within a forward facing arc because it is obstructed by the superstructure of the ship as illustrated by FIG. 2. A radar may be similarly obstructed. These areas in which a weapon or sensor system is ineffective are termed `blind arcs` and impose constraints on the ships heading to ensure that all threats can be engaged successfully without the targets allocated to each weapon entering the blind arc of the tracking radar or the weapon.
A problem arises in that a plan view display is not always the most convenient form of presentation, and it becomes difficult for the commander to recognise manoeuvre options from this kind of display when there are several potential problems to consider simultaneously. This situation may arise for example if there are two or more targets to be engaged and also possibly a collision risk to be considered. A simple plan view display can be made to present all of the necessary information, including the relative positions and velocities of targets and other objects, and the weapon and sensor system coverage, but in the plan-view form it can be difficult to recognise the options available for the best course to steer.
Other forms of display are in common use. For example it is common practice in submarine command and control systems to present active sonar information in cartesian coordinates of range and bearing and to present sensor information representing the position and possibly the velocity of objects such as other ships and aircraft.